"More than 30% of patients received a cumulative estimated effective dose of more than 100 mSv, (millisievert) a level at which there is little controversy over the potential for increased cancer risks," they wrote.
The patients in the study underwent a median of 15 procedures involving radiation exposure, and of those four were high-dose procedures, equal to the amount of radiation one would be exposed to from the environment during one year.
Nearly 20% of the patients had at least three MPIs and 4.9% had at least five.
The volume of MPI testing increased from fewer than 3 million procedures in 1990 in the U.S., to 9.3 million in 2002, and "is now estimated to account for more than 10% of the entire cumulative effective dose to the U.S. population from all sources, excluding radiotherapy," they wrote.
For 39% of the patients who underwent more than one MPI, the dose was 121 mSv, "higher than that in the exposed (greater than or equal to mSv) cohort in the Life Span Study of Japanese atomic bomb survivors," they wrote.
The researchers do not suggest that the tests were inappropriate, and in fact emphasized that "the clear majority of MPI examinations were performed for reasons presently regarded as appropriate, and with the potential to effect therapeutic management."